Detection of IgM-rheumatoid factor and anti-citrullinated protein antibodies in healthy horses and their comparison.

This research paper investigates the presence of rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA) in healthy horses of different ages. The study aims to establish the potential use of these factors, traditionally associated with rheumatoid arthritis (RA) diagnosis in humans, in the diagnosis of equine diseases with similar symptoms to RA.

Background on Rheumatoid Factor and Anti-Citrullinated Protein Antibodies

• RF, particularly IgM-RF, is a traditional marker used in both human and veterinary medicine to support the diagnosis of RA. It refers to the antibodies that the immune system produces in response to inflammation which is commonly associated with rheumatoid arthritis.
• ACPA has been added to the grading system for diagnosing RA in humans in recent years. These are antibodies produced by the body’s immune system that target proteins (citrullinated proteins) which have undergone a specific transformation due to inflammation.
• The newer diagnostic criteria that include ACPA have emerged due to RF’s limitations in diagnostic capacity. These include an increased RF titration in humans suffering from non-rheumatoid diseases, a failure to predict RA, and excessively high titers in older populations.

Idiopathic Polysynovitis in Horses and The Use of RF and ACPA

• Clinical observations of horses with idiopathic polysynovitis, a condition that presents similar symptoms to human RA, raised queries about the potential use of RF and ACPA diagnostic tools in horses. Idiopathic polysynovitis refers to an inflammation of multiple joints in the horse without a known cause.
• In this study, the serum levels of IgM RF were assessed in 60 clinically healthy horses, ranging in age from 3 days to 30 years. Additionally, 55 of these horses were tested for ACPA using ELISA methods to measure Anti-CFG (Anti-Citrullinated Fibrinogen Antibody).

Findings of the Study

• The research concludes that there is an age-dependent increase in IgM RF levels, which peaks around the age of 9 years.
• On the other hand, the presence of ACPA was found to be independent of the horse’s age.
• Furthermore, both markers — IgM RF and ACPA — were found to be independent of the horse’s gender, indicating that male and female horses are equally likely to produce these antibodies.